Hard water explained

What is
hard water?

Hard water is a common problem in millions of homes across the UK, but to many, its origin is a mystery. Learn what we mean by hard water, what causes water to become hard, and how it differs to soft water – all in our handy guide.

A common problem

6 out of 10 homes in the UK have hard water

Hard water

Hard water is any water that contains high levels of magnesium and calcium minerals. These minerals are naturally present in soil and sedimentary rock, and as water flows through the ground, they dissolve and enter the water supply.

The more minerals present, the harder the water.

What makes water hard?

Certain regions of the UK are prone to hard water because of their underlying geology. Areas rich in limestone and chalk, for example, will often produce harder water because these rocks dissolve at a higher rate, releasing more minerals.

What is soft water?

In contrast, soft water is any water that contains zero or low levels of dissolved minerals. Naturally soft water is typically found in areas with non-porous rock, like granite, where rainwater flows across the surface without absorbing much mineral content.

How hard is the water in your area?

If you want to know exactly how hard the water is in your home, enter your postcode into our hard water checker below, or book a free home survey with your local Kinetico water expert.

Is hard water bad?

Hard water isn’t necessarily bad in its own right – it’s safe to drink and millions of homes around the UK use hard water on a daily basis.

However, it can cause problems, not least from the buildup of limescale in your pipes and appliances. This can significantly impact your energy efficiency, lead to costly repairs, and even reduce the lifespan for washing machines, dishwashers, kettles, and boilers. Skin and hair issues, such as dryness or irritation, are also often made worse by hard water.

Poor energy efficiency

A buildup of limescale can cause heating systems to work harder, increasing energy use.

Dry skin and eczema

Hard water can strip natural oils from the skin, worsening dryness and irritation.

Damaging to appliances

Mineral deposits can shorten the lifespan of household appliances like kettles and dishwashers.

Worse for the environment

Hard water increases the use of cleaning products and energy, causing a larger environmental footprint.

How is water hardness measured?

In the UK, water hardness is typically measured in parts per million (ppm) or milligrams per litre (mg/l) of calcium carbonate (CaCO3) – so, the full value will usually be either ‘ppm CaCO3’ or ‘mg/l CaCO3’. This value reflects the amount of dissolved calcium and magnesium in the water, which causes the hardness.

While ppm and mg/l are the most common metrics, you might also encounter “degrees Clark” or “grains per gallon” (gpg) – particularly in the US.

Below is a guide to water hardness levels, using ppm CaCO3:

Water Hardness (ppm CaCO3)	Water Type
0-60	Soft
61-120	Moderately hard
121-180	Hard
181+	Very hard

What softens water?

The most effective method for softening water in your home is installing a water softener. At Kinetico, our water softeners use a scientific process called ion exchange to remove the minerals that cause water to become hard. This process replaces the calcium and magnesium in hard water with sodium ions, effectively softening the water before it reaches your taps.

How water softeners work